Isolation, Purification, and Properties of Malate Dehydrogenase from Sulfur Bacterium Beggiatoa leptomitiformis

Malate dehydrogenase (E.C. 1.1.1.37) from the bacterium Beggiatoa leptomitiformis was isolated and purified 123-fold using a five-step purification procedure including the enzyme extraction, ammonium sulfate protein fractionation, gel filtration, ion exchange chromatography, and gel chromatography. The enzyme was homogenous according to the electrophoresis data; its activity was 20.43 U/mg protein. This malate dehydrogenase is a homotetramer (Mr = 172 kDa). The catalytic and thermodynamic properties, as well as the analysis of the published data suggest that the tetrameric structure of the enzyme allows it to participate in constructive metabolism supplying the cell with organic acids as a source of carbon.